The present invention relates to electromagnetic wave capturing devices which detect electromagnetic waves including radiation such as X-rays, visible light, and infrared light. The invention also relates to composite active matrix substrates for use in the electromagnetic wave capturing devices, and methods for manufacturing the composite active matrix substrates.
Conventionally, an active-matrix substrate, which is provided with pixel electrodes and switching elements disposed in a two-dimensional manner, finds wide application in devices such as a display device and a capturing device. For example, demand for the active matrix substrate as monitors for an audio/visual device and an office automation device has been rapidly increasing. Examples of such a display device and a capturing device include liquid crystal display devices (LCDs: Liquid Crystal Displays), which are expected for application to a flat TV, and x-ray capturing devices (FPXDs: Flat Panel X-ray Detectors), which are capable of directly reading out x-ray images in the form of electric signals without an film.
The active matrix substrate for use in such a display device and a capturing device includes thin film transistors (TFTs) of metal wiring and semiconductor, which are precisely arrayed in a matrix pattern on an insulating substrate such as a glass substrate. Manufacture of the active matrix substrate requires highly sophisticated processing techniques such as photolithography and expensive manufacturing equipment. This has made it difficult to manufacture a large-area active-matrix substrate because the yield dropped drastically as the area or resolution of the active-matrix substrate was increased. Another problem is that once the manufacturing equipment is built, it is impossible to manufacture an active-matrix substrate which is larger than the substrate size suitable for the manufacturing equipment. That is, it has been difficult to manufacture a large active-matrix substrate to accommodate the increased size of display devices or capturing devices.
As a counter-measure for these problems, there have been proposed methods of forming a composite active-matrix substrate by connecting a plurality of small active-matrix substrates. For example, xe2x80x9cLarge Area Liquid Crystal Display Realized by Tiling of Four Back Panels (Proceedings of the 15th International Display Research Conference (ASIA DISPLAY ""95, pp. 201-204 (1995)))xe2x80x9d (reference 1) discloses an arrangement of a composite active-matrix substrate for use in liquid crystal display devices. Further, U.S. Pat. No. 5,827,757 (reference 2), published on Oct. 27, 1998, discloses a method for manufacturing a composite active-matrix substrate and an x-ray capturing device utilizing the composite active-matrix substrate.
The active-matrix substrate described in the above reference 1, as shown in FIGS. 13(a) through 13(c), is fabricated as follows: after four small active-matrix substrates 101, with their element bearing sides 101a facing down, are aligned on a stage 103 with a vacuum chuck, a back side (upper side in FIG. 13(a)) of the active-matrix substrates 101 is bonded to a base substrate 102 with an adhesive resin 105. Here, the adhesive resin 105 contains a spacer 104. Further, an ultraviolet curable resin is used for the adhesive resin 105.
Meanwhile, the composite active-matrix substrate described in the above reference 2, as shown in FIGS. 14(a) through 14(g), is made up of a plurality of small active-matrix substrates 111 bonded to a base substrate 112. Specifically, this composite active-matrix substrate is fabricated in the following manner: after an edge of the active-matrix substrate 111 whose element bearing side is covered with a protecting film 121 is cut by dicing and polished (see FIGS. 14(a) and 14(b)), the plurality of active-matrix substrates 111, with their element bearing sides facing down, are aligned on a stage 113 and connected to each other with an adhesive resin 141 which fills a gap between the active-matrix substrates 111 (see FIGS. 14(c) and 14(d)). Thereafter, a back side (upper side in FIG. 14(d)) of the plurality of active-matrix substrates 111 is bonded to a base substrate 112 with an adhesive resin 131. Then, after the active-matrix substrates 111 are removed from the stage 113, the protecting film 121 is peeled off from the active-matrix substrates 111 (see FIGS. 14(e) through 14(g)). Here, formation of a large number of orderly openings (holes for releasing an adhesive resin) 112a prevents air bubbles from being trapped in the adhesive resin 131 which fills a spacing between the active-matrix substrate 111 and the base substrate 112, and helps excess adhesive resin 131 to escape.
However, the foregoing conventional composite active-matrix substrates and manufacturing methods have the following problems. For example, the composite active-matrix substrate described in the reference 1 appears to be manufactured in such a way that the plurality of active-matrix substrates 101 aligned together, coated with the adhesive resin 105 having fluidity, are bonded to the base substrate 102. Here, the plurality of active-matrix substrates 101 must be bonded with the base substrate 102 in a state where a distance between these two substrates is at the distance of a gap determined by a spacer. This causes a problem that the adhesive resin 105 seeps out (pressed out) of the active-matrix substrate 101. As a result, it becomes difficult to prevent air bubbles from being trapped in the adhesive resin 105, and cleaning of the excess adhesive resin 105 will be required. This results in a problem that workability suffers significantly.
On the other hand, in the composite active-matrix substrate described in the above reference 2, theoretically, a large number of openings 112a formed in advance on the base substrate 112 can prevent air bubbles from being trapped, and excess adhesive resin 131 can escape through the openings 112a when the base substrate 112 and the active-matrix substrate 111 are bonded. However, in cases where a comparatively large composite active-matrix substrate is to be manufactured, the base substrate 112 cannot be pressed down (toward the active-matrix substrate 111) uniformly over the surface when it is bonded. This results in a problem that air bubbles and the adhesive resin 131 cannot be released properly at portions of the base substrate 112 where the applied pressure is weaker, or at thinner portions of the base substrate 112. In addition, forming the large number of openings 112a on the base substrate 112 increases manufacturing costs. Further, cleaning of excess adhesive resin 131 which has seeped out through the opening 112a is still required, resulting in a problem that workability suffers significantly.
Further, in the composite active-matrix substrate described in the above reference 2, a rubber squeegee (not shown) is used to fill a gap between the small active-matrix substrates 111 with the adhesive resin 141. This causes problems that the adhesive resin 141 is likely to spread to the top surface (element bearing side) of the active-matrix substrate 111, and an external force is applied to the active-matrix substrate 111 through the rubber squeegee. Thus, filling of the adhesive resin 141 required an extremely thick protecting film 121 which covered the top surface of the active-matrix substrate 111.
An object of the present invention is to provide a composite active-matrix substrate of a structure in which a plurality of small active-matrix substrates are fixed on a base substrate, which can be fabricated without such deficiencies as seeping of an adhesive resin (adhesive filler) used to fix the small active-matrix substrates, or trapping of air bubbles. Another object of the present invention is to provide a method for manufacturing such a composite active-matrix substrate, and to provide an electromagnetic wave capturing device using such a composite active-matrix substrate.
In order to achieve this object, a composite active-matrix substrate according to the present invention includes: a plurality of active-matrix substrates, each having a top surface with an active element, which are disposed adjacent to one another so that the top surfaces of the active-matrix substrates make up a substantially level surface; a base substrate, which is provided so as to oppose a bottom surface of the active-matrix substrates; a sealant, which is provided in the form of a frame between the bottom surface of each active-matrix substrate and the base substrate; an adhesive filler A, which fills a spacing surrounded by the base substrate, the sealant, and each active-matrix substrate; and an adhesive filler B, which fills a gap between edges of the active-matrix substrates which are disposed adjacent to one another.
With this arrangement, the sealant prevents seeping of the adhesive filler A, and therefore prevents surface contamination of the active-matrix substrates due to adhesive filler A, thereby realizing a composite active-matrix substrate with each active-matrix substrate firmly fixed on the base substrate.
Further, in order to achieve the foregoing object, another composite active-matrix substrate according to the present invention includes: a plurality of active-matrix substrates, each having a top surface with an active element, which are disposed adjacent to one another so that the top surfaces of the active-matrix substrates make up a substantially level surface; a base substrate, which is provided so as to oppose a bottom surface of the active-matrix substrates; a gel sticking material, which is provided between the bottom surface of each active-matrix substrate and the base substrate, for combining each active-matrix substrate with the base substrate; and an adhesive filler B, which fills a gap between edges of the active-matrix substrates which are disposed adjacent to one another.
With this arrangement, since the adhesive filler used to fill a spacing between each active-matrix substrate and the base substrate is the gel sticking material which has high flexibility but no fluidity, the adhesive filler does not contaminate the surface of each active-matrix substrate, and a composite active-matrix substrate with each active-matrix substrate firmly fixed on the base substrate can be provided.
Further, in order to achieve the foregoing object, another composite active-matrix substrate according to the present invention includes: a plurality of active-matrix substrates, each having a top surface with an active element, which are disposed adjacent to one another so that the top surfaces of the active-matrix substrates make up a substantially level surface; a base substrate, which is provided so as to oppose a bottom surface of the active-matrix substrates; a double-sided adhesive sheet, provided between the bottom surface of each active-matrix substrate and the base substrate, having a top surface and a bottom surface respectively provided with sticking layers for combining the base substrate with each active-matrix substrate; and an adhesive filler B, which fills a gap between edges of the active-matrix substrates which are disposed adjacent to one another.
With this arrangement, since the adhesive filler used to fill a spacing between each active-matrix substrate and the base substrate is the double-sided adhesive sheet of a solid form, the adhesive filler does not contaminate the surface of each active-matrix substrate, and a composite active-matrix substrate with each active-matrix substrate firmly fixed on the base substrate can be provided.
In order to achieve the foregoing object, an electromagnetic wave capturing device according to the present invention includes: one of the foregoing composite active-matrix substrates; a conversion layer, provided on the top surface of the active-matrix substrates, for converting an electromagnetic wave into electrical charge; and a bias applying electrode layer provided on the conversion layer.
Further, in order to achieve the foregoing object, another electromagnetic wave capturing device according to the present invention includes: one of the foregoing composite active-matrix substrates; a scintillator, provided on the top surface of the active-matrix substrates, for converting an electromagnetic wave into light; and a photo-electric conversion element, provided on the active-matrix substrates, for converting light into electrical charge.
With either arrangement, because the composite active-matrix substrate is composed of a plurality of active-matrix substrates tiled together, a large-area yet inexpensive electromagnetic wave capturing device can be provided.
In order to achieve the foregoing object, the present invention provides a method for manufacturing a composite active-matrix substrate which includes: a plurality of active-matrix substrates, each having a top surface with an active element, which are disposed adjacent to one another so that the top surfaces of the active-matrix substrates make up a substantially level surface; and a base substrate, which is provided so as to oppose a bottom surface of the active-matrix substrates, the method including the steps of: forming a sealant in the form of a frame between the base substrate and the bottom surface of each active-matrix substrate, so as to connect the base substrate with each active-matrix substrate via a sealant; and injecting an adhesive filler A into a spacing surrounded by the base substrate, the sealant, and each active-matrix substrate through an opening which opens into the spacing through at least one of the base substrate, the sealant, and each active-matrix substrate.
With this method, the adhesive filler A is prevented from seeping out of a spacing surrounded by the sealant, and therefore the adhesive filler A does not contaminate the surface of the active-matrix substrate, thereby further improving the efficiency of using the adhesive filler A and the efficiency of combining each active-matrix substrate with the base substrate.
Further, in order to achieve the foregoing object, the present invention provides another method for manufacturing a composite active-matrix substrate which includes: a plurality of active-matrix substrates, each having a top surface with an active element, which are disposed adjacent to one another so that the top surfaces of the active-matrix substrates make up a substantially level surface; and a base substrate, which is provided so as to oppose a bottom surface of the active-matrix substrates, the method including the steps of: providing a gel sticking material between the base substrate and the bottom surface of each active-matrix substrate; and combining the base substrate and the active-matrix substrates with the gel sticking material.
With this method, since the adhesive filler is a gel sticking material which has high flexibility but no fluidity, the adhesive filler does not contaminate the surface of the active-matrix substrate when combining the substrates. In addition, the gel sticking material, because it is flexible, can completely fill the gap between the substrates.
Further, in order to solve the foregoing object, the present invention provides another method for manufacturing a composite active-matrix substrate which includes: a plurality of active-matrix substrates, each having a top surface with an active element, which are disposed adjacent to one another so that the top surfaces of the active-matrix substrates make up a substantially level surface; and a base substrate, which is provided so as to oppose a bottom surface of the active-matrix substrates, the method including the steps of: providing, between the base substrate and the bottom surface of each active-matrix substrate, a double-sided adhesive sheet having a top surface and a bottom surface respectively provided with sticking layers; and combining the base substrate and the active-matrix substrates with the double-sided adhesive sheet.
With this method, since the adhesive filler is a double-sided adhesive sheet of a solid form, the adhesive filler does not contaminate the surface of the active-matrix substrates when the substrates are combined.
Further, in order to solve the foregoing object, the present invention provides another method for manufacturing a composite active-matrix substrate which includes: a plurality of active-matrix substrates, each having a top surface with an active element, which are disposed adjacent to one another so that the top surfaces of the active-matrix substrates make up a substantially level surface; and a base substrate, which is provided so as to oppose a bottom surface of the active-matrix substrates, the method including the steps of: fixing the active-matrix substrates on the base substrate so that the top surfaces of the active-matrix substrates disposed adjacent to one another make up a substantially level surface; and injecting an adhesive filler B by capillary action between edges of the active-matrix substrates which are disposed adjacent to one another, so as to bond the active-matrix substrates with one another.
With this method, the adhesive filler B can fill a gap between edges of the active-matrix substrates without causing the adhesive filler B to stick to the top surface of each active-matrix substrate and without externally applying any physical force onto the surface of each active-matrix substrate.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.